docs: def _raise_invalid_gzip_err(self):
          """ A gzip file with multiple ARC/WARC records, non-chunked
          has been detected. This is not valid for replay, so notify user
          """
          frmt = 'warc/arc'
          if self.known_format:
              frmt = self.known_format
  
          frmt_up = frmt.upper()
  
          msg = self.GZIP_ERR_MSG.format(frmt, frmt_up)
          raise ArchiveLoadFailed(msg)